The AASHTO (originally AASHO) pavement design guide was first published as an interim guide in 1972. Updates to the guide were subsequently published in 1986 and 1993. The AASHTO design procedure is based on the results of the AASHO Road Test conducted from 1958-1960 in Ottawa, Illinois.

Approximately 1.2 million axle load repetitions were applied to specially designed test tracks in the most comprehensive pavement test experiment design conducted to that point. The original AASHO design process was strictly empirical in nature; subsequent updates have included some mechanistic provisions, such as, classifying the subgrade stiffness in terms of resilient modulus and accounting for seasonal variation in material stiffness.

AASHO design originated the concept of pavement failure based on the deterioration of ride quality as perceived by the user. Thus, performance is related to the deterioration of ride quality or serviceability over time or applications of traffic loading.

Also developed at the AASHO Road Test was the rendering of cumulative traffic loading in terms of a single statistic known as the 18-kip equivalent single axle load (ESAL).

The 1993 AASHTO Guide for Design of Pavement Structures is the only approved design method for CPCD projects at TxDOT. This design produces a rigid slab thickness in inches required to support the estimated traffic under a selected serviceability interval and estimated support and environmental conditions. The design procedure is available in automated form in the AASHTO DARWin® 3.1 program and Web Application at .

For more information on using the AASHTO CPCD design procedure, refer to the

1993 AASHTO Guide for Design of Pavement Structures

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Reinforcing steel design is reflected in the department’s recommended CRCP and CPCD standards, found under the Pavements section on the

The TxCRCP-ME and AASHTO DARWin® 3.1 programs are available to TxDOT personnel through the district pavement engineer. Consultants may obtain the TxCRCP-ME program from the district pavement engineer or the Pavement Asset Management Section of the Maintenance Division.